Vascular endothelial growth factor-A, matrix metalloproteinase-1, and macrophage migration inhibition factor changes in the porcine remnant kidney model: evaluation by magnetic resonance imaging

Blood outgrowth endothelial cells reduce hypoxia-mediated fibroblast to myofibroblast conversion by decreasing proangiogenic cytokines

PURPOSE

Hypoxic conditions cause fibroblasts to differentiate into alpha smooth-muscle cell actin (α -SMA)-positive cells, i.e. myofibroblasts. This process is a hallmark of venous neointimal hyperplasia (VNH) associated with hemodialysis vascular access. The purpose of this study was to determine if blood outgrowth endothelial cells (BOEC) may reduce the conversion of fibroblasts into myofibroblasts under hypoxic conditions, and to determine the potential mechanisms involved.

METHODS

An experimental model was used, in which fibroblasts and BOEC were subjected to hypoxia under contact and transwell conditions to determine if BOEC reduce the conversion of fibroblasts into myofibroblasts under hypoxic conditions. Gene expression under different conditions was performed. In addition, functional assays including cell proliferation and migration were determined.

RESULTS

This study demonstrates that contact needs to occur between BOEC and fibroblasts for the reduction of the hypoxia-driven conversion of fibroblasts into α-SMA. This is associated with a decrease in several proangiogenic genes including vascular endothelial growth factor A, platelet-derived growth factor, fibroblast growth factor and matrix metalloproteinase 2 in fibroblasts in contact with BOEC when compared to fibroblasts alone. In addition, migration is significantly reduced while proliferation remains unchanged.

CONCLUSION

This study helps provide rationale for using BOEC delivered to the adventitia of the outflow vein of hemodialysis vascular access to reduce VNH.

Novel therapies for hemodialysis vascular access dysfunction: myth or reality?

Hemodialysis vascular access dysfunction is a major source of morbidity for patients with ESRD. Development of effective approaches to prevent and treat vascular access failure requires an understanding of the underlying mechanisms, suitable models for preclinical testing, systems for targeted delivery of interventions to maximize efficacy and minimize toxicity, and rigorous clinical trials that use appropriate outcome measures. This article reviews the substantial progress and ongoing challenges in developing novel treatments for arteriovenous vascular access failure and focuses on localized rather than systemic interventions.

Reproducibility of MRI renal artery blood flow and BOLD measurements in patients with chronic kidney disease and healthy controls

PURPOSE

Determine the reproducibility of renal artery blood flow (RABF) and blood-oxygenation level dependent (R2 *) in patients with chronic kidney disease (CKD) and healthy controls.

MATERIALS AND METHODS

RABF and R2 * were measured in 11 CKD patients and 9 controls twice with 1- to 2-week interval. R2 * in the cortex and medulla were determined after breathing atmospheric air and 100% oxygen. Reproducibility was evaluated by coefficients of variation (CV), limits of agreements and intra-class coefficient calculated by variance components by maximum likelihood modeling.

RESULTS

Single-kidney RABF (mL/min) for patients was: 170 ± 130 and 186 ± 137, and for controls: 365 ± 119 and 361 ± 107 (P < 0.05 versus patients), for first and second scans, respectively. RABF measurements were reproducible with a CV of 12.9% and 8.3% for patients and controls, respectively. Renal cortical R2 * was: 13.6 ± 0.9 and 13.5 ± 1.2 in patients (CV = 8.0%), and 13.8 ± 1.6 and 14.0 ± 1.5 in controls (CV = 5.6%), while medullary R2 *(s(-1) ) was: 26.9 ± 2.0 and 27.0 ± 4.0 (CV = 8.0%) in patients, and 26.0 ± 2.4 and 26.1 ± 2.1 (CV = 3.6%) in controls, for first and second scans, respectively. In both groups R2 * in medulla decreased after breathing 100% oxygen.

CONCLUSION

The reproducibility was high for both RABF and R2 * in patients and controls, particularly in the cortex. Inhalation of 100% oxygen reduced medullary R2 *.

Expression of profibrotic genes in a murine remnant kidney model

PURPOSE

To test the hypothesis that there is increased expression of several profibrotic genes, including matrix metalloproteinase (MMP)-2 and MMP-9 and tissue inhibitors of metalloproteinase (TIMP-1 and TIMP-2), a disintegrin and metalloproteinase with thrombospondin motif-1 (ADAMTS-1), and fibroblast specific protein-1 (FSP-1) in a murine remnant kidney model.

MATERIALS AND METHODS

Chronic kidney disease (CKD) was created in 10 C57BL/6 male mice (20-25 g) by performing a right nephrectomy and ligation of the upper pole of the left kidney (remnant kidney). Animals were sacrificed 42 days and 56 days later. Reverse transcriptase polymerase chain reaction (RT-PCR) for MMP-2, MMP-9, TIMP-1, TIMP-2, ADAMTS-1, and FSP-1 was performed in the remnant kidney. Histologic evaluation of the remnant kidney was performed using Ki-67, α-smooth muscle cell actin (α-SMA), hematoxylin and eosin, and Masson' trichrome staining. Kidney function was assessed using serum blood urea nitrogen (BUN) and creatinine.

RESULTS

The mean serum BUN and creatinine levels at day 42 and day 56 were significantly higher than baseline (P < .05). By day 42, the mean expression of MMP-2, MMP-9, TIMP-1, ADAMTS-1, and FSP-1 was significantly higher in the remnant kidney compared with the normal kidney (P < .05); by day 56, only FSP-1 expression was significantly higher (P < .05). There was increased fibrosis by Masson' trichrome, increased Ki-67, and increased α-SMA staining in the remnant kidney compared with the normal kidney.

CONCLUSIONS

In the remnant kidney, there was increased fibrosis with increased α-SMA and Ki-67 staining and significantly increased expression of MMP-2, MMP-9, TIMP-1, ADAMTS-1, and FSP-1.